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EARNINGS PER SHARE - Antidilutive Securities (Details) - $ / shares	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Feb. 13, 2020
Class A Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Exchangeable notes, exchange price per share (in USD per share)	$ 40.87		$ 40.87
Warrants sold in connection with the issuance of the exchangeable notes (in USD per share)					$ 62.88
Restricted Class A Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (shares)		2,949		8,965
Class B Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (shares)	10,131,878	10,229,142	10,188,369	10,884,874
Out-of-the-money Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (shares)	4,547,783		5,201,394
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (shares)	716,276	1,678,774	724,484	1,531,722
Out Of The Money Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (shares)		2,100,833		2,419,305